Drivers in Texas, Iowa, and Indiana will enjoy higher speed limits next month as legislation raising the top speeds on rural roads takes effect.

On Friday, Texas Governor Rick Perry (R) signed HB 2257 into law making 80 MPH the maximum allowable speed in the state. Rural portions of I-10 and I-20 will enjoy the new top speed, while other rural roads could see the limit rise to 75 MPH. Both the state House and Senate adopted the legislation without opposition last month.

On July 1, a law signed by Iowa Governor Tom Vilsack (D) creating a 70 MPH speed limit goes into effect. This new limit better reflects the actual speed of cars on rural highways which averages 69.8 MPH according to sensors embedded into the pavement.

In May, Indiana Governor Mitch Daniels (R) signed SB 217 into law raising the maximum limit from 65 MPH to 70 MPH in areas with less than 50,000 population. The law also raises the limit for trucks from 60 to 65 MPH, and gives a 10 MPH boost to several roads currently posted at 55 MPH. The state will begin placing the higher-limit signs on July 5.

Highway gas mileage stickers are based on an EPA test conducted on what amounts to a treadmill at an average speed of 48mph. There is no air resistance and unrealistic rolling resistance. Accessories such as AC are off. Acceleration is limited to about 3mph per second, or 0-60 in 18 seconds. To try and account for these inadequacies, results are then tweaked downwards by an arbitrary 22% irrespective of model.

The test is so divorced from actual driving as to be absolutely meaningless to the consumer, and the occasional instances where EPA numbers match real driving are purely coincidental.

Well, they have done studies on this i believe 55 is the most efficient use of gas.

Very outdated information from the 70's compiled from biased testing. In the 70's a car doing 60 mph was turning around 3500 rpm's or higher. Today my SUV will do 75 mph without going over 2100 rpm's.

During the summer I drive to work from the lake quite often. Traffic in the fast lane moves consistently at 75 to 80 mph and see almost no unsafe driving incidents. About once a week someone will hang in the fast lane doing 68 mph and all hell breaks loose. You see more unsafe driving incidents in 10 minutes than you see in a week at the higher speeds.

Recent studies show that the safest traffic pattern on non-urban highways is when the lanes move at the speed which 80% or more of the drivers want to travel at. Traveling at other rates of speed increase tension, increase reaction time and promote compulsive actions.

I drive Dallas to Shreveport about once a month, but I use US 80 out to MP 500 and pick up I-20 there. The limit has been 60 or 65 on the US 80 and even part of I-20 for several years. I rarely see more than one vehicle pulled over anywhere.

I drive a 1995 Toyota 4WD pickup, 3 liter V-6, manual 5-speed, 113,000 miles. For years I drove 70-75 on this run, but since gas passed $2, on the last couple of trips I tried to hold 65, hard to do exactly without cruise control, but I'm now actually seeing 20 mpg rather than 18.5. I have replaced the cat converter with an aftermarket one that probably causes less back pressure, and it also got me through the Dallas area emissions inspection with a much better score than last year's squeak-by with the original stock one.

My trip now takes me 15 minutes longer, but if I start 15 minutes earlier, it works out the same, right?

I was passed at night on I-10 between Beaumont and Houston doing 85, and the speed limit at night was 70 (75 in day). 100+mph driving will become more and more commonplace. Not that I have a problem doing so safely, but too many other drivers (regardless of age) are not as compotent behind the wheel as I am...

Modern hell? My 83 Cutlass has a '73 455 in it with an overdrive tranmsission and on the highway I get 26 mpg going 75-80mph.. It drops to 20-22 mpg in the 60-65 mph range. Of course I don't have steep rear gears (2.21 open rear).

HIGHWAY gas mileage stickers are actually quite accurate. Whatever they post on the sticker for highway speeds is tested at HIGHWAY SPEEDS... often 75 mph or so.

Actually, and I can find the link if you like, the EPA hwy mileage ratings are based on a loop that involves some speeding up and slowing down, and a top speed of 55. The test simulates a 10 mile trip and averages 48 mph. At steady speeds, like out on the interstates in rural areas, especially with the cruise control set, many cars can do better than the EPA hwy ratings at speeds of 65-75.

WHy don't they do the thick concrete for road construction nationwide (at least on interstates)? I know down in Louisiana they do, and they don't have to do much road work other than lane widening or bridge work but once every ten years or so, even with all the trucks on the road. This asphalt stuff may be cheaper, but I think with all the $$ poured into that, it would save to do concrete.

Auxillary transmission coolers are a snap to put on. just bypass the line out from the radiator for the fluid from going straight back to the transmission, go to the cooler, and out from there back to the transmission. Or if you don't want it to be tied to engine temperature at all, just run it directly bypassing the radiator altogether both ways(however running it through the radiator first helps in winter). I have run my 455 powered Cutlass w/ a 2004r overdrive (a transmission that three shops told me should not be behind a big block) regularly up and down the highway, some at 90+ mph, as well as some thrilling 1/4 mile runs, some sanctioned at tracks some well, i plea the fifth, and the only thing ever to go wrong is I had to replace a defective 2nd gear band... But guess what, I still get 26 mpg hwy in the speed range everyone practically drives at...

Power to weight ratio has a lot to do with it too. If you have relatively high power vehicle with a relatively low weight (12-15 lbs per hp), as long as it is not geared too steep or accelerating too hard to get up to speed, decent fuel economy is essentially a given, and while youre right wind resistance does increase geometrically, it doesn't overcompensate for a decent power/weight ratio in detracting from fuel economy. Add the higher speed/fuel efficency powerband, and the fuel efficency factor is not adversely effected by speed unless you are way up there in velocity, like 95+mph or more.

From Nashville TN to Baton Rouge, LA, going I-40, I-55, and I-12/10, doing 65 on the trip down I averaged 20.98 mpg. From Baton Rouge back to Nashville, I did 75-85 most of the way, depending on where I was (didn't do much over 80 in TN for fear of the lawman), and I got 26.35 mpg.

One summer day a few years ago, I was on 465 headed west to I65 (no 865 then) and was going 80 mph just to keep from getting run over. This was about 3:30 in the afternoon, so traffic was starting to pick up.

About the time I got to Michigan Road, I saw an Indy cop had someone pulled over--while the rest of us continued to fly by. How the h*ll the cop picked this guy out of all of us to ticket, I will never know.

170
posted on 06/28/2005 7:02:50 AM PDT
by IN Farm Girl
(Hoosier by birth, Boilermaker by the grace of God)

Even with the opportunity to drive MUCH faster, most drivers won't do it because of the focused intensity of the task at hand.

After 100 mph in the Civic, I have to concentrate hard. It's quite tiring, actually, to sustain that amount of concentration for very long. But I did get from Mobile to Tallahassee in 3 hrs once. That's an average of 80 mph. In Atlanta I routinely drive over 80 dang near out of necessity.

174
posted on 06/28/2005 7:18:32 AM PDT
by numberonepal
(Don't Even Think About Treading On Me)

Recent studies show that the safest traffic pattern on non-urban highways is when the lanes move at the speed which 80% or more of the drivers want to travel at. Traveling at other rates of speed increase tension, increase reaction time and promote compulsive actions.

I'm NOT complaining about safety at all. Would just like to see a new study of the fleet to find the average most efficient speed and go with that.

The problem as I see it is that the driver that I described is *ALWAYS* passing. There is no one on the road that is going faster so he rules the left lane, and even those of us who are *ALSO* passing but (not at his speed) have to dodge out of his way. Then he tries to convince us that *WE* are the law breaker because we don't get out of his way faster. That is a prime example of pissing on someones leg and trying to convince them that it is raining.

Would just like to see a new study of the fleet to find the average most efficient speed and go with that.

About two years ago, in a settlement with EPA, they tried to force a 55 mph speed limit for Houston and the surrounding suburban counties. To show the appropriate emissions savings they used EPA's modplan IV. This was an outdated plan. However, using modplan V showed no savings and using the very newest plan showed a degradation. The particular emissions measured are directly proportional to the amount of fuel burned. Ergo, EPA's latest figures show increased fuel consumption when speed is reduced from 70 mph to 55 mph. Houston Metro area Speed limits are back up to 70 mph.

Frankly, I think the only safe place to go at top speeds are in rural areas like Wyoming and Montana without much other traffic and with safe vehicles and tires. I'm concerned about these trucks as well. I'm perfectly happy at 65-70 mph. It also saves fuel. We'll see.

There are other major factors beside wind resistance at play, and if you only look at one factor of course you will get the wrong impression. The efficiency of an engine can vary dramatically across its range, with the optimally efficient speeds being set by the design engineers -- even taking into account wind resistance.

To put it another way, the increase in wind resistance from 60 MPH to 70 MPH is less than the differences in effective output and efficiency of the engine in that same range. Wind resistance is far from being the whole story.

The whole point of diesel-electric rigs or hybrid engines is that the engine can always be running at its optimal efficiency point by decoupling engine output from motion on the road. Even given the significant losses in two-stage conversion process, the much higher efficiency of the combustion engine running optimally more than compensates.

183
posted on 06/28/2005 8:26:01 AM PDT
by tortoise
(All these moments lost in time, like tears in the rain.)

There are several intersections along Interstate 10 between Van Horn and Sierra Blanca. This is the first one of them. This section of Interstate 10 is among the least traveled of the highway's length across the southern tier of the country. (Photo taken 3/14/04)

There is a picture of a yellow diamond-shaped sign clearly denoting an intersection on I-10.

Yes, but the use of the term intersection is somewhat misleading in those cases. Instead of on/off ramps, the road does 'intersect' at just one side, but the critical difference is that no traffic can cross the interstate. Instead the only movements available are right turns, and there is no light or stop sign impeding movement on the interstate. By law, a road can't be an interstate if the main lanes are impeded by such. The only exceptions are a couple (IIRC) of drawbridges.

Explain how the autobahn is one of the safest roads in the world despite no speed limit at all?

They give people tickets for passing on the right, and for driving in the left (passing) lanes. We should do that here and we could make our roads much safer. It is much more organized to drive in Europe where everyone is keeping right except to pass.

In Florida I'd be fraid of rubber gators much less real ones for high speed fun runs.....not to mention the little gators in court..........LOL !

If ya have a system to beat the DPS speed traps share it if ya will .....

I have a friend that is stuffing a viper engine in a dodge magnum station wagon. He go the body in a semi dented condition cheap and just "bought" the viper engine outright. It is IMHO the current day version of the old Nomad. When he's done I'll post a few pictures.

People allow others to pass ny getting the heck out of the left lane. If more jerks would move right to allow faster traffic by, the roads would be safer for all concerned. That's how it works on the Autobahn.

Have you been on I-10 between Houston and San Antonio? Once you get past the greater Houston area (read past Katy) 85-90 is about normal. They don't play and they move over when someone is approaching.

100+ in a Crown Vic? No way... sloppy feel of the steering in one of those babies... unless they've improved that greatly... Just way too easy to oversteer in one of those base fresh off the assembly line. Maybe if it has a sports package that inproved road feedback and feel....

I can and have done well over 100mph, but on a public road in traffic, 80ish is tops for me... of course if I lived out west where the Highways are all flat and straight and drone on forever I might be more comfy at higher speeds... here, where you are going around, over or through a mountain to get anywhere, 80's is fine.

most modern ones get their optimal fuel efficiency in the 70-75 MPH zone

My BS meter is pegged. Maybe it needs recalibration. I know someone's recently been pushing the idea that, for every 1 MPH over 55, it's like adding a nickel to the price of a gallon of gasoline (which is just a way of quantifying the point that fuel economy is worse). Obviously, that's intended to be a very rough average.

Seems to me that the optimal state for fuel economy is the slowest speed at which the engine is turning "relatively effortlessly" in the highest gear. I could be wrong but, it seems like for most modern cars, on flat terrain in no wind, that's between 40 and 50 MPH.

I think that's where my cars with trip computers show their highest fuel economy readings. At any rate, you've given me reason to check. And, I understand those trip computers don't really measure MPG. Mine have proved to be fairly close, though.

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